1. Field of the Invention
The present invention relates to a packaging device and a method of manufacturing the packaging device, such as a chip tantalum capacitor, in which the base and tip sides of a portion of a lead terminal, not molded in resin are bent nearly along an external surface of the resin.
2. Description of the Prior Art
FIG. 1 shows a package structure of a conventional tantalum capacitor T'. Numeral 10 represents a chip of the capacitor T'. As conventionally known, an electrode is formed at each of an external surface and a central portion of the chip 10. To the two electrodes, lead terminals 11 and 12 are connected, respectively. The connection of the electrode provided at the external surface of the chip 10 to the lead terminal 11 is made by soldering one end of the lead terminal 11 directly to the electrode surface. The connection of the electrode provided at the central portion of the chip 10 to the lead terminal 12 is made through a tantalum wire 13 protruding from the electrode.
The chip 10 whose electrodes are connected to the lead terminals 11 and 12, respectively, is molded in a resin 14 together with the tantalum wire 13 and one end portion of each of the lead terminals 11 and 12. Conventionally, the outline of the cross section of the resin 14 is, schematically describing, like a pair of vertically symmetrical trapezoids connected to each other. Each of the lead terminals 11 and 12 horizontally protrudes from a portion corresponding to an edge of the connection portion of the trapezoids.
In assembling the tantalum capacitor T' having such a structure onto a circuit board as an element of an electronic circuit, portions 11A and 12A (hereinafter referred to as terminal out-of-resin portions) of the lead terminals 11 and 12 which portions are not molded in the resin 14 are L-shapedly bent nearly along an external surface of the resin 14. These portions serve as connection portions to the circuit board.
FIGS. 2A to 2C sequentially show a conventional process of forming bent portions on the terminal out-of-resin portions 11A and 12A. As shown in FIG. 2A, the terminal out-of-resin portions 11A and 12A protrude straight at the point of time when base portions of the lead terminals 11 and 12 are molded in resin.
To form the bent portions on the terminal out-of-resin portions 11A and 12A, a forming roller FR' made of tool steel abuts against a predetermined position of the terminal out-of-resin portions 11A and 12A when it moves so as to draw a predetermined locus while rotating in the vicinity of the terminal out-of-resin portions 11A and 12A fixed by chucking the upper and lower surfaces of the resin 14 with an appropriate chucking apparatus (not shown), and it forcibly bends the abutted portion along the locus.
That is, the terminal out-of-resin portions 11A and 12A protruding from both end surfaces of the resin 14 are formed into an almost L shape along the external surface of the resin 14 by nearly perpendicularly bending their base portions 11a and 12a downward and further by nearly perpendicularly bending predetermined portions 11b and 12b located on the tip side of the base side bent portions 11a and 12a inward. In the forming process, first, as a primary process, tire tip side bent portions 11b and 12b of the terminal out-of-resin portions 11A and 12A are formed as shown in FIG. 2B.
The locus of the forming roller FR' in the primary process is not shown. When the roller FR' passes through a position a predetermined distance away from the end surface of the resin 14, the tip side portions of the terminal out-of-resin portions 11A and 12A abut against the roller FR' and are forcibly, perpendicularly bent downward as the roller FR' moves, thereby forming the tip side bent portions 11b and 12b. A portion of the terminal out-of-resin portion 11A between the end surface of the resin 14 and the tip side bent portion 11b and a portion of the terminal out-of-resin portion 12A between the end surface of the resin 14 and the tip side bent portion 12b are supported on flat surfaces, respectively.
Then, as a secondary process, the base side bent portions 11a and 12a of the terminal out-of-resin portions 11A and 12A are formed as shown in FIG. 2C. In this secondary process, the forming roller FR' draws a locus L' passing in the vicinity of the end surface of the resin 14, and in a process similar to the primary process, it nearly perpendicularly bends the base portions of the terminal out-of-resin portions 11A and 12A downward with the end surface of the resin 14 as a fulcrum S1, thereby forming the base side bent portions 11a and 12a. Conventionally, the base side portions 11a and 12a are bent in a condition where edges are formed since an admission angle .theta.1 of the forming roller FR' is set to approximately 80.degree. and the distance between the fulcrum S1 and the forming roller FR' are set to be extremely small.
In connecting the lead terminals 11 and 12 to an electrical connection on a circuit board by soldering, the tantalum capacitor T' of such a structure is pressed on the upper surface of the resin 14. Moreover, there are occasions when a similar pressing force acts from the outside after the connection to the circuit board is completed. In such cases, the pressing force is concentrated on the base side bent portions 11a and 12a of the terminal out-of-resin portions 11A and 12A.
However, in a case where the base side bent portions 11a and 12a of the terminal out,of-resin portions 11A and 12A are nearly perpendicularly bent so as to constitute edges like the above-described prior art, since a stress is concentrated on the bent portions 11a and 12a when the pressing force is applied, cracks are apt to be generated. Because of this, under a condition where the package has been assembled on a circuit board, there is a strong possibility that the package breaks at the base side bent portions 11a and 12a due to a deteriorated mechanical strength of the lead terminals 11 and 12 at the portions 11a and 12a. There is also a strong possibility that the package breaks due to an external force which acts after the assembly is completed. If the lead terminals break, it will be impossible for the capacitor to perform its function.